A newlywed policeman killed on duty was due to go on honeymoon next week.
PC Andrew Harper, married to wife Lissie in July, was hit by a car while on a burglary call.
Ten people are being held on suspicion of murder.
The distraught uncle of PC Andrew Harper paid tribute to his nephew saying the whole family had been left “devastated” by his death.
Dale Shrimpton said: “He’s my oldest nephew. My sister’s first born. Mum and dad’s first grandson... and was married two weeks ago.
“We are devastated. He was the loveliest person that you will ever meet. I can’t begin to tell you how we feel.”
PC Harper was allegedly hit by a car and dragged under it on Thursday night, while responding to a burglary call.
The 28-year-old died at around 11.30pm, near the A4 Bath Road, between Reading and Newbury, at the village of Sulhamstead, Berks.
Ten people, including a 13-year-old boy, were tonight being quizzed on suspicion of murder, Thames Valley Police said.
Chief Constable John Campbell said: “What we do know is Andrew had been dragged along by a vehicle.”
He said PC Harper had got out of his marked police car, leaving his colleague in the vehicle, when he was allegedly struck and killed.
Aerial pictures showed skidmarks on the road and a blood trail, with a grey BMW on a verge nearby.
Officers yesterday raided a traveller site near Burghfield Common, around two miles from the scene.
A force spokesman said: “This police presence in Four Houses Caravan Park forms part of the investigation following the death of PC Andrew Harper.
“Officers are at the scene making enquiries.”
Three police vans remained at the site tonight.
Dept Chief Con Jason Hogg said the force was “devastated at the loss of our colleague”.
And Prime Minister said the tragedy was a “powerful reminder” of the bravery displayed by officers on the streets every day.
PC Harper had been due to go on honeymoon next with his wife, Lissie, after their “dream wedding”.
Pictures show the couple celebrating their big day at Ardington House, a Georgian manor in Oxfordshire.
One shows them smiling as they cut their wedding cake alongside a sign saying “happily ever Harper”.
Last week Lissie shared a picture of her beaming at Andrew with the caption: “Happiest day imaginable.”
Describing Andrew as her “best friend”, Lissie wrote on Facebook : “I can’t believe our wedding was almost two weeks ago, we have just had a sneaky peak of some of our photos from our amazing photographer.
“Thank you so much to everyone who came and who helped to make it the most perfect day.”
PC Harper is the first officer killed on duty since March 2017, when unarmed PC Keith Palmer was stabbed by Khalid Masood during the Westminster bridge terror attack.
As investigations continued tonight, detectives were going through audio and video of the incident taken from the car-mounted and body-worn cameras.
A forensic tent had been set up behind the BMW in the apparent spot where PC Harper died.
Officers laid two bunches of flowers at the scene and Mr Campbell said the force’s flags were flying at half mast in his honour.
A postmortem was being carried out this afternoon to establish the cause of death.
PC Harper’s grandmother, Maureen Shrimpton, also spoke of her grief. She said: “Just a really horrible day.
“Our grandson Andrew was killed while doing his police work.
“So proud of him. Our love goes to his lovely wife, mum, dad, brother and all his family and friends. Love Nan and Bubba xxx.”
PC Harper joined the force as a special constable in 2010 and became a police officer a year later.
Serving in the roads policing proactive unit based at Abingdon police station, he was a “highly regarded, popular member of the team”, Mr Campbell said.
His death represented a “significant loss” to Thames Valley Police and “also to his colleagues and friends”, he added.
Mr Campbell said: “The officer was well-known across the force so it is felt very personally by the whole police family across the UK.”
He paid tribute to other officers and members of the fire and ambulance services who attended “what was obviously a distressing scene”.
It comes after PC Gareth Phillips was run over by a suspected car thief in Birmingham last week. The married 42-year-old West Midlands traffic officer is said to be have suffered “potentially life-changing” injuries.
Mr Campbell said police were facing rising levels of violence
He said: "In these extreme circumstances, it's resulted in the loss of Andrew's life, so from that point of view, is policing getting more violent?
"There's a challenge for society in terms of the easy recourse to violence.
"But from a policing point of view, we know there are associated risks."
Boris Johnson said he was “deeply shocked and appalled” by the death of “brave” PC Harper.
He said: “My thoughts are with PC Harper’s family, friends and colleagues at this terrible time.
“It is the most powerful reminder that police officers up and down the country put themselves at risk every single day to keep us safe. They have my absolute support.”
Andy Fiddler, from the Thames Valley Police Federation, said it was "totally devastating", adding: "All our toughs are with the family, friends and close colleagues of PC Harper."
Shadow Home Secretary Diane Abbott said she was “incredibly saddened” by PC Harper’s death.
The Labour MP added: “All my thoughts are with the family, friends and colleagues of the courageous PC Andrew Harper.”
Richard Benyon, Conservative MP for newbusy, said it was an "absolute tragedy" and he hoped "those responsible would will be brought to justice".
Anyone with information should call police on 101.
Analysis: Make sure that we learn from awful incident
By Peter Kirkham, ex-Met Police Detective Chief Inspector
The horrendous murder of PC Andrew Harper raises questions about how the danger to police officers doing their job is managed.
For now our thoughts are with his family, colleagues and friends, but we must also make sure lessons are learned from this tragedy.
Full details of the awful incident are not known but some things are clear. PC Harper was responding to reports of a burglary even though he was a roads policing officer.
With so few patrols in many rural areas now this is not unusual – the nearest patrols attend, regardless of their actual role.
It is not clear whether he and his colleague attended the scene of the burglary and encountered the suspects leaving, or whether they spotted them being driven away.
What is known is that at some point PC Harper was struck and fatally injured by a vehicle, presumably as he attempted to stop it and speak to the occupants.
Injured
There has been no mention of whether other police units were in attendance, but it would not surprise me to find he and his colleague were on their own.
Sadly it is getting ever more common for offenders in vehicles to deliberately drive at or over police officers who try to stop them.
Just a week or so ago PC Gareth Phillips was seriously injured in such an incident in the West Midlands force area.
This incident and the attack on Metropolitan Police constable Stuart Outten, 28, who was stabbed by a suspect allegedly armed with a machete in Leyton, East London shows just how vulnerable to attack our patrolling officers are.
The cuts to police numbers mean there is less assistance available and it is often further away when every minute counts.
The devastating murder of PC Harper highlights the risks that brave officers across the country take every day to keep us all safe.
The new Government urgently needs to make sure their promises about increasing the numbers of police officers actually happen.
