RIVERSIDE, Calif. (KABC) -- Police in Riverside were searching for the gunman who killed a 7-Eleven clerk during an attempted robbery early Friday morning that may be connected to two other crimes in the area.A customer found the clerk, a man in his 30s who had succumbed to his injuries, in the store in the 6600 block of Indiana Avenue around 3:20 a.m., police say.Investigators are trying to determine when the shooting occurred.AIR7 HD was over the scene, where a cash register drawer on the ground behind the counter appeared to be damaged and opened."We do believe that this was probably some type of robbery attempt during which the victim was murdered," said Riverside police Ofc. Ryan Railsback.Police were investigating two robberies at other 7-Eleven locations in the county. Authorities have not yet said if the shooting and robberies are connected."A 7-Eleven in Moreno Valley and a 7-Eleven in the city of Perris that were robbed, we believe at gunpoint. Other than the fact that those two along with this one are all 7-Eleven's, that's the only link we have right now," Railsback said.The victim's identity is being withheld until his next of kin is notified, but one woman who is a regular customer said she knew the clerk. Carol Sfakis said she knew the clerk and spoke to him the night before as he was arriving to work."I don't understand why they'd wanna kill him. It doesn't make sense," she said.Sfakis said she would sometimes stay at the store and keep the clerk company but didn't Thursday night, instead going home to rest.She added that the victim is the father of two young children."He has two kids; he told me that the other day. And he said 'Those are my life, those are my babies,'" Sfakis said.Detectives will review surveillance video to determine if the suspect acted alone and to investigate a possible connection between the three 7-Eleven robberies.