We talked to the store owner, who was the only one to escape last night's shooting unharmed.
Tony Amer: "He kept telling me not to move or else he'll shoot me."
Store owner Tony Amer says he was behind the counter when a man wearing a motorcycle helmet pulled out a gun and shot his co-worker Yahya who he calls Isaac, and a 45 year old customer.
Tony Amer: "He just said give me change for a dollar that's all he asked for, when I got to the cash register, I started giving him change all I heard was the shots."
The 19 year old store clerk was shot and killed.
He and the critically wounded off-duty security guard were rushed to the hospital.
Amer says neither of the men said anything to provoke the violence.
Tony Amer: "He was sitting on the computer-focusing on what he was doing on the computer, he didn't say a word. The Mexican guy didn't say a word even the killer didn't say a word all he said was give me change for a dollar-that's all he said. After I went down to cover from the shots I thought he was going to shoot me too. I went down and he was on top of me already and he said don't move or I'll kill you too that's all he said."
Police say the robber took money from the register and rode off on his motorcycle.
They don't think either victim was targeted but are investigating what caused the robber to fire so quickly.
Lt. Shannon Galvan, Fresno Police: "There's lots of things that could have happened- he could have been startled for some reason. Until we can complete the investigation, who knows what happened."
The store's owner says Isaac was a family friend who just started working for him in the last three weeks.
Counselors were on hand Tuesday at Roosevelt High School where he attended.
The mini-mart he worked at does money transfers and check cashing right across the street from Scandinavian Middle School.
Macy Vang, Neighbor: "We go there a lot for little things like we ran out of milk or eggs or sugar for things like that, and a lot of kids go there too."
The store has had problems in the past.
In June 2005 a man was shot and killed in the parking lot.
The killer still hasn't been caught.
Police right now only say he was wearing motorcycle gear.
They won't say if any surveillance video is helping their investigation.
Police say this is the first time in seven years a store clerk has been killed in a robbery.
Meanwhile the security guard shot remains in critical condition.