Walker says a third man, 21-year-old Devon Bond, was arrested last week. Bond is also a Drexel student.
Police say the robbery happened at a woman's apartment around 10:30 p.m. Wednesday.
According to investigators, Phillip called Bond to his room at University Crossings and they, along with Harris, left for the robbery scene together.
Once there, police say Bond tried the door of the victim's home, but it was locked. He then ordered chicken wings from a restaurant below the apartment, paying with a credit card. Police say surveillance video from that restaurant, along with his credit card information, later helped identify him.
Police say he rang the doorbell at the woman's apartment and, through the intercom, Bond was able to talk his way into the apartment by saying he knew the victim's male roommate.
On his way in, Bond propped the door open with a newspaper. A few minutes later Harris and Phillip, who were armed with handguns, go inside, police said.
One of the players then forced Bond to the ground as part of a ruse to make it look as if he was being robbed, Walker said.
Police say Harris and Phillip then demanded money at gunpoint, walking the woman around looking for cash.
"Weapons were drawn as they entered into the room," Lt. Walker said. "They came right toward the victim with the gun pointed at her and were making the demands throughout, threatening they would return if they didn't find the money.
When they couldn't find any money, they allegedly left with two cell phones.
"We think the roommate of the victim was being targeted," Walker said. "We believe Bond knew that there was money in that apartment."
After the female student reported the robbery, Bond told police he had been the victim of a crime, Walker said. Police quickly found out that wasn't true, Walker said, and determined he had plotted the robbery with Harris and Phillip.
Police tried to arrest Harris and Phillip over the weekend, but they could not be found. They turned themselves in on Monday, and police expect to charge them later in the day.
Harris, a 5-10 point guard out of New York City, started all 32 games for the Dragons last season and averaged 14.5 points a game. Phillip, a 6-6 forward from Brooklyn, averaged 2.9 points and 3.1 rebounds coming off the bench in 31 games.
Police said they have no idea why Harris and Phillip would participate in this robbery. Harris' attorney, Robert Lynch, said his client is looking forward to his day in court.
"He's an excellent student, comes from a great family from New York. He's never been in trouble in his life," Lynch said.
He went on to question the source of the allegations, though refused to say if the person he's referring to was the victim.
"The sources of these allegations are corrupt, and the evidence will show that down the line," said Lynch.
As for Harris' future, Lynch was confident he will beat the charges.
"We look forward to cooperating with Drexel and any questions that have with us, and we expect he'll continue to be a successful student and basketball player."
In a statement, Drexel officials said all of the students were suspended during this investigation, and that the Department of Public Safety is fully cooperating with the Philadelphia Police Department.
The Associated Press contributed to this report.