"Certainly, that is on the table," Vaden said at a news conference.
Kawin Brockman, 19, of Conway; Kelcey Perry, 19, of Morrilton; Mario Toney, 20, of Little Rock; and Brandon Wade, 20, of Lake Village, also face charges of attempted capital murder, eight counts of terroristic threatening, and gun violations.
They are accused of killing Ryan Henderson, 18, of Little Rock, and Chavares Block, 19, of Dermott. Martrevis Norman of Blytheville was wounded in the leg but has been released from the hospital.
Investigators declined to offer many details of the shooting Sunday night at the campus in Conway, about 30 miles north of Little Rock.
The men appear to have driven up on a group of students near the Arkansas Hall dormitory and fired at least eight rounds from a semiautomatic pistol, campus police Lt. Preston Grumbles said. He declined to say whether or not multiple handguns were used.
"It appears that they were not the intended targets," Grumbles said. "It appears that, at this time in the investigation, that they were no way involved in the motive that we're formulating."
While Vaden declined to elaborate, he said the defendants each has some sort of criminal record.
So far, some suspects have spoken with investigators about the night of the crime, while others have remained silent, the prosecutor said.
"This is an incredibly heinous case," Vaden told reporters. "When you have a situation where it appears some, if not all of the victims were innocent bystanders, that's bad."
The men remain held in the Faulkner County jail without bond pending a court hearing. Police declined to identify their lawyers. Telephone numbers registered in Perry's and Toney's names were disconnected. A number for Brockman could not be found. A man who answered a number in Wade's name said the defendant was not represented by a lawyer. The man declined to comment.
The university resumed classes Tuesday, with students mostly quiet as they walked through the autumn chill. More than 300 students, faculty members and Conway residents filed into an auditorium in the afternoon to remember the two slain students. Those entering passed a pair of enlarged photos of the two slaying victims - Henderson looking at the camera with a pensive look on his face, hands clasped; Block posing in an all-white suit at his 2006 high school prom.
"We will move forward," Wendy Holbrook, associate dean of students, told those gathered. "We will not forget."
Students swayed to "Amazing Grace" and later stomped and clapped to a gospel ballad.