More than 500 people gathered at Howard University’s Andrew Rankin Memorial Chapel on Wednesday evening to remember Omar Adam Sykes, a rising senior who was shot and killed during an attempted robbery just outside the campus July 4.

Relatives, friends, Howard officials and Mayor Vincent C. Gray spoke about the student, who had turned 22 days before his death.

“This just simply should not have happened,” Gray said to the packed chapel as he chastised federal lawmakers for not taking “sensible steps” to keep guns off the streets.

Gray also said at the service that police had made an arrest recently in the June 1 burglary of Sykes’s Northwest Washington apartment. Police have not indicated any connection between that burglary and Sykes’s death nearly five weeks later. No one has been arrested in the slaying.

At the memorial service, Sykes’s grandmother and uncle led a pledge of nonviolence, and Howard President Sidney A. Ribeau implored the mourners to help stop similar crimes across the country.

“The violence in our cities, the crimes against our young people must stop,” Ribeau said. “This is a moment in time where we must recommit ourselves to the values that Omar lived by.”

Kinaya Grayson, Sykes’s girlfriend, recalled hours of conversations they had. The couple didn’t have a romantic story about where they first met, she said, or their anniversary — which they made up as April 8 because neither could remember the date.

“For him, I’m not going to be sad and I’m not going to be angry,” she said. “I still might cry.”

Tsega Mekonnen Meshesha, a friend of Sykes’s for more than a decade, first met him when they both lived in Ethiopia. “To me, he was my family, he was my blood,” she said. “My blood, my rock, my confidant. My God, this list could go on forever.”

As she read a letter to Sykes, she began choking up.

“You wouldn’t want me to stand here crying,” she said. “Because you always say I’m ugly when I do.”

Sykes’s older sisters, Halima Sykes Dumas and Jamila Sykes, described their reactions to a new baby brother — who was “white as a sheet” at birth with long black hair, according to Sherry Zalika Sykes, their mother.

“As the big sister, I never knew what to do with this boy creature,” Dumas said to laughter. “He just did everything his way.”

Sykes was determined to chart his own course, his family said, and relentlessly pursued his myriad passions, including writing, art, music and business.

He never sat still and never stopped talking, they recalled, often prompting letters home from grade-school teachers asking for advice.

But if he was stuck in a class that didn’t interest him, they said, he would quickly nod off.

“Omar was just as good at sleeping as he was talking,” his mother said to chuckles.

Sykes and another student were attacked about 11:30 p.m. at Georgia Avenue and Fairmont Street NW, Howard officials said. Police said two men with handguns approached the students and announced a robbery. Sykes was shot and the other student was struck with a gun in what police have said was a random crime.

Authorities said Wednesday that they had no updates on the case.

Since September, Howard University police have documented a small spike in violent crime, including armed robberies, thefts and assaults, on and around the university’s open campus near Georgia Avenue. A student was the victim of a carjacking in a campus parking lot in the fall.

Despite the increase in violent crime, Howard University Police Chief Leroy James said in the fall that overall crime in and around the school had decreased. Since James took over in 2008, robberies have dropped from 47 to 29 in 2010, 22 in 2011 and 14 as of October 2012.