Ismael's predecessor at the Masjid Musa Mosque, who was gunned down in August 2012, had been accused of aiding al-Shabab, including recruiting youths for the Somali group.
"While it's possible the timing is linked, the pattern of targeted killings and disappearances in Mombasa long predates Westgate. What's clear is that a serious independent investigation of yesterday's killing and earlier attacks on Aboud Rogo and others is urgently needed to answer the many questions about these attacks," Leslie Lefkow, an Africa researcher at Human Rights Watch said.
The dark four-door car that Ismael was riding in was riddled by bullets. People gathered around the car, taking photographs and staring at the bodies as weeping relatives of the dead approached.
Police spokeswoman Gatiria Mboroki denied that police had any involvement in the killings. "We are investigating who did this and what the motive is because we don't know," she said.
Human rights groups estimate that Kenyan police were responsible for approximately 1,000 extrajudicial killings between 2008 and 2012, according to the U.S. State Department.
"Members of the security forces were suspected of being responsible for a number of forced disappearances. At least half dozen prominent Muslim leaders alleged to have terrorist ties were victims of killings or forced disappearances," the State Department said, in its annual report on human rights.
Young men on Friday partly burned the Salvation Army Church and put burning tires on the road. Police carrying assault rifles came to the scene as smoke poured from the compound. Police fired into the air and lobbed tear gas. Kenya's Red Cross said four people were killed in the rioting, including at least one with gunshot wounds.
Supporters who had gathered around the scene of Ismael's assassination Thursday blamed Kenyan police for the deaths, saying the killings were payback for the Westgate Mall attack in Nairobi.
"If we take up arms we are terrorists, if we don't we get killed ... what are we supposed to do when they are killing us. The police are killing us," said Sheik Abubaker Shariff Ahmed also known as Makaburi, who has been sanctioned by the United Nations and the U.S for alleged links to al-Shabab.