Two masked men exchanged a glance and a nod before opening fire on a group of college students who had turned over their wallets and cell phones, a man who was with the victims said Monday.

The cold-blooded manner of the gunmen alarmed police, who said they may have shot three other men in less than a week, sometimes without robbing them.

The three wounded college students, who remained hospitalized Monday, gave Denver police descriptions of the suspects that matched those in three previous predawn shootings.

"Someone knows who's doing this, and they need to come forward," said Denver police spokeswoman Virginia Quiñones.

Ian Dumpert, 22, of Paola, Kan., was in serious condition, while John Watt, 22, of Wamego, Kan., and Joseph Kuebel, 23, of Glen Ellyn, Ill., were in fair condition, said Dee Martinez, Denver Health spokeswoman.

They were shot around 5 a.m. Sunday while waiting with four friends for the light rail at 25th and Welton streets after attending a music show at the nearby Cervantes Centerpiece Ballroom.

One of the friends said the gunmen approached them and demanded their wallets and told them to put them on the ground. Then, they asked for their cell phones, he said.

After everyone complied, the robbers began shooting, striking Dumpert in the face and Watt in the chest. The victims' friend said the robbers ran, but turned to fire two more shots, hitting Kuebel in the back and grazing his leg.

The Rocky Mountain News is withholding the friend's name because he is a witness.

Police reports released Monday showed that in each of the incidents two masked suspects shot their victims, and not necessarily to rob them.

At about 5:10 a.m. Friday, at 541 E. 14th Ave., two suspects were in a blue Honda with tinted windows when they shot a 27-year-old man in the leg.

Ten minutes later, at an alley near 1402 Pearl St., two suspects, on foot, shot a 26-year-old man in the foot and leg.

Just before 2 a.m. Saturday at 1085 Colorado Blvd., two suspects walked up to a 35-year-old man and shot him several times after demanding money and being told he didn't have any. The victim was taken to Denver Health Medical Center in serious condition. His status was not known Monday."Any incident like this is of a high level of concern for our organization," Quiñones said.

The two suspects are described as black men wearing ski masks or blue bandannas. One is 6-foot-2 to 6-foot-4, about 180 to 190 pounds, and possibly has a pockmarked face. The other is 5-foot-8 to 5-foot-10, about 180 pounds with short black hair.

morenoi@RockyMountainNews.com or 303-954-2895