A man has been arrested in connection with the murder in London of an imam who was a critic of Syrian President Bashar al-Assad, police said Monday.

Abdul Hadi Arwani, 48, was found in his car with gunshot wounds to the chest in Wembley, northwest London, on Tuesday. The investigation into his death is being handled by counter-terrorism police.

Scotland Yard said a 36-year-old man had been arrested on suspicion of conspiracy to murder and remains in police custody. They had previously given the man’s age as 46.

Arwani, 48, was a staunch opponent of Syrian President Bashar Assad, and was involved in violent protests against the regime leader in 2011. 

The cleric was witness to the violent 1982 Hamas massacre by the Syrian Army under Assad’s father, Hafez al-Assad; up to 40,000 civilians are estimated to have been killed in those events.

Arwani was deeply affected by the massacre. He was given a death sentence for photographing the carnage and damage, and his family fled Syria for the UK shortly after that. 

The cleric recently stepped down – or was forced to step down, according to some sources – as imam of the An-Noor Mosque in Acton, West London, after the mosque was associated with extremism and Islamism. 

But several associates insisted to the Daily Mail that Arwani was a moderate Muslim who shunned extremism and was a down-to-earth, mild, modest person who was a prominent community leader in London. 

A police source told the Mail that the killing appeared to be a “state-sponsored assassination” and the mosque’s reputation may have preceded him. 

Terrorist Mohammed Ahmed Mohamed changed in the mosque into a burka and fled, and has been missing since 2013. 

Uthman Mustafa Kamal, the son of hate preacher Abu Hamza, has regularly led prayers at An-Noor as well; another preacher delivered an infamous anti-Semitic sermon there in 2012. 

Police say they are “open-minded” about the motive for his killing – although one source involved in the case said last week that the death had all the signs of a state-sponsored assassination. 

Arwani’s son Murhaf called his murder a “heinous” crime and appealed for anyone with information to come forward.

“We know that it won’t bring our father back to us but it may help to deliver justice to those who killed him,” he added.

AFP contributed to this report.