UNION GROVE, Wis. — Three Illinois men who were shot to death at close range during a drag racing event in southeastern Wisconsin may have been targeted by a rival gang member, but a lack of cooperation has stymied the investigation, sheriff’s officials said on Monday.

The three were fatally shot as they stood near a concession area in the parking lot of the Great Lakes Dragaway near Union Grove about 7 p.m. Sunday, according to Kenosha County sheriff’s officials.

The shooter remains at large, Sheriff David Beth said Monday.

‘‘Some of the family members, some of the people involved, are not very cooperative with law enforcement,’’ Beth said on WTMJ-AM. “And that’s making it more difficult to investigate this whole thing.’’

Sergeant Mark Malecki said that the victims were from the Aurora area in Illinois.

‘‘The victims were known gang members,’’ Malecki said, adding that deputies were investigating the possibility that the assailant was a rival gang member.

ASSOCIATED PRESS