The victims were Muslim, and the FBI is now investigating whether race or religion played a role in the slayings.
Deah Shaddy Barakat, 23; his wife, Yusor Mohammad Abu-Salha, 21; and her sister Razan Mohammad Abu-Salha, 19, were killed Tuesday in the couple's Chapel Hill apartment.
The couple met while helping to run the Muslim Student Association at N.C. State, before Barakat moved to Chapel Hill to study dentistry at UNC. Yusor Abu-Salha, who graduated in December, planned to enroll in the dental school in the fall. Razan Abu-Salha, still at N.C. State, was visiting from Raleigh when they were killed.
Police have said the trio was gunned down Tuesday after a long-running dispute over parking.
The victims' neighbor, Craig Stephen Hicks has been charged with three counts of first degree murder.
UT Dallas students said the vigil wasn't only about sending their prayers and respects to the three victims; it was also a chance for the community to channel their emotions in a positive way to stand against injustice.
"It's beautiful seeing people from different cultures and backgrounds all here for a humanitarian cause," said UT student Huda Hashim. "This isn't political, religious or anything. It's to mourn and support each other."
A similar, much larger gathering is expected to take place Friday night at Dealey Plaza at 6 p.m.
The Associated Press contributed to this report.