CHICAGO (Reuters) - A man who was wounded in a shooting at an Illinois warehouse last month has sued the state police for wrongly allowing the shooter to buy the handgun he used to kill five co-workers and injure others, local media said.

Timothy Williams, an employee at Henry Pratt Company in Aurora, 40 miles (65 km) west of Chicago, was shot three times during the rampage, the Chicago Tribune said on Friday, citing the lawsuit. He is seeking $2 million, the newspaper said.

Williams could not immediately be reached for comment and Illinois State Police declined to comment, saying it does not respond to questions about pending litigation.

The gunman, Gary Martin, 45, carried his pistol to work on Feb. 15 and opened fire on fellow employees after being told he was being dismissed from the company. Five co-workers were killed and five police officers and a sixth employee were wounded before Martin died in a gunfight with police.

Illinois Governor J.B. Pritzker, a Democrat, vowed to seek tighter gun control measures after it emerged that Martin, a convicted felon, had wrongly been granted a firearms permit and allowed to buy a pistol, but was never forced to surrender the weapon after the mistake was realized.

On Wednesday, Illinois State Police announced improvements to their processes, including sharing firearms data with other law enforcement agencies in the state and increasing enforcement of Firearm Owners Identification (FOID) laws and penalties.

Martin purchased the .40-caliber Smith & Wesson with a laser sight in March 2014 using a FOID card issued two months earlier, even though his status as a convicted felon should have barred him from obtaining the card.

His card was revoked later that month, after he requested a concealed-weapons permit that triggered a more thorough check, including fingerprinting, that revealed his 1995 aggravated assault conviction in Mississippi.

Police said they have no record of any effort to ensure Martin surrendered his FOID card or weapons, as required, after he was told by letter that he was supposed to relinquish them.