Malaysian police say they are still hunting for two suspects in the murder of the Palestinian engineering professor Fadi al-Batsh on the weekend.
But if, as many suspect, the alleged killers are agents with Israel's Mossad intelligence service, they may never be found.
Hamas, the Islamist group that runs Gaza, say the engineer was assassinated.
In Kuala Lumpur, Malaysian police held up composite images of the two men suspected of gunning down al-Batsh on the weekend.
Malaysia's inspector general of police Mohamed Fuzi Harun conceded there was not much to go on.
"The sketch shows two light-skinned suspects who are European or Middle Eastern," he said.
Mr Harun went on to say that both men had beards that were "quite long", and were about 180 centimetres with sturdy builds.
Malaysia said it suspected a foreign intelligence agency was involved, and Hamas quickly pointed the finger at Mossad.
Hamas said al-Batsh was an important member.
Al-Batsh's uncle said two people on a motorbike pursued his nephew.
"When they made sure that he was Fadi al-Batsh they fired 10 bullets at him," he said.
Israel has officially denied any involvement.
Security analysts said that was standard procedure.
The 'secret war' between Israel and Hamas
Yoni Ben Menachem, a senior researcher at the Jerusalem Centre for Public Affairs, said according to Israeli and Palestinian security sources, al-Batsh was helping Hamas develop weapons.
"He was specialising in drones, and also helping the Palestinian military wing of Hamas to make its rockets more accurate," he said.
Some suspect al-Batsh may have also been assisting with submarine drones that could strike offshore oil and gas platforms.
Mossad was also the prime suspect when a prominent Palestinian drone expert was killed in Tunisia in 2016.
Mr Menachem said behind the scenes the war between Israel and Hamas has never ended.
"There is for a long time a clandestine war, a secret war between Israel and Hamas — and actually it's a race," he said.
"Hamas wants to surprise Israel with new weapons and tactics in the next war, and Israel is trying to prevent it.
"This is what's going on, and what we see is part of it."
