A second 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 Tuesday, according to AFP.

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

Police said Tuesday that a 61-year-old man was arrested on suspicion of conspiracy to commit murder, the second arrest in the case.

Earlier, 36-year-old Leslie Cooper was charged with Arwani’s murder and appeared in court before being remanded in custody, according to a police statement.

Cooper is due to appear at London’s Central Criminal Court later this week.

Police said they were searching the An Noor mosque in Acton in West London, where Arwani was a preacher from 2005 to 2011.

“We have been in contact with trusted community Muslim advisors this afternoon to reassure them that the action is necessary and that the premises will re-open as quickly as possible,” London police said in a statement quoted by AFP.

Arwani reportedly fled Syria as a teenager after surviving the 1982 Hama massacre, in which the current president’s father Hafez Al-Assad sent troops to brutally crush an Islamist-led uprising.

Police say they are “open-minded” about the motive for his killing.

Arwani’s son Murhaf thanked police for their “swift investigation” and urged anyone with information to come forward.

“Your cooperation will help us close this painful page and begin to move on with our lives, in the knowledge that the person who took away our father, will be brought to justice and duly punished for this heinous crime,” he said in a statement.