RENO, Nev. -- A gunman who police said was about to be fired surrendered Friday after shooting three co-workers at a Walmart store in Nevada in a possible retaliation attack, authorities said.

The surrender came after police negotiators spoke for two hours by telephone with 45-year-old John Dennis Gillane as he was holed up in the back of the store.

Gillane was taken into custody and will be charged with three counts of attempted murder, Reno police Lt. Mohammad Rafqat said.

No shots were fired after the three victims, including a manager, were wounded shortly after 8:30 a.m., police said.

"I'm very happy he is out and the situation didn't escalate," Rafqat said. "We convinced him the best move was to surrender."

Rafqat did not know how many shots were fired or whether Gillane said anything at the time of the shootings.

"Today was going to be the day he was going to address his employment situation," he said.

Police had not established a motive for the shooting but suspect it was related to the termination, Reno Deputy Police Chief Mike Whan said.

At least nine heavily armed officers entered the store more than an hour before the surrender of Gillane, who police believe had a handgun.

One of the victims was critically wounded, but "the prognosis is good for all of them," said Dan Fogleman, a spokesman for Wal-mart Stores Inc. He provided no further details.

Police originally described all the injuries as non-life threatening but later said they were not sure that was the case.

One victim was treated and released, Rafqat said. Another was in critical but stable condition, and the third was in serious condition.

Employees were placed on a bus in the parking lot of a sporting goods store next to the Walmart.

Washoe County deputies, Sparks police and the FBI joined Reno police in sweeping the store to be sure there were no hostages.

Jack McDonald, 64, of Reno said he works as a greeter at the store but was not there during the shooting.

"There are some strange people who work here, but I can't think of one who would be a vicious enough person to do something like this," McDonald said. "This has to be a personal thing."