DETROIT -- A Detroit Police Academy graduation began on a sorrowful note Friday, as new officers and their families mourned for a toddler killed in an act of "senseless violence" a day earlier.

The ceremony, held at Greater Grace Temple, included a moment of silence for Amiracle Williams, the 3-year-old killed in a shooting Thursday that officials say was sparked by a fight on social media.

In his speech to the graduates, now tasked with policing the city, Detroit Police Chief James Craig said he stood in front of them "with a heavy heart."

"When we think about the loss of our young angel, Amiracle Williams, the tragedy of someone so young ... we fight for all, we fight for our young," Craig said.

Four others were wounded in the shooting on Detroit's east side, Craig said after the ceremony. Amiracle's mother, 40, father, 47, and sister, 17, were injured in the incident, which took place in front of the Williams' home on Mogul Street near Hayes. One of the suspects, a 22-year-old black male, was also shot and injured.

Amiracle's father is believed to have shot one of the victims, Craig said.

A dispute on Facebook culminated in a confrontation outside the Williams residence, where several young women had a physical fight Thursday afternoon, police said. The father, observing the fight, "felt his daughters may have been in some sort of danger and responded by shooting one person at the scene," Craig said.

After the first shooting, a second individual took out a machine gun and began to fire repeatedly, striking Amiracle and her three family members, he said.

As of 3 a.m. Friday, police had two suspects under arrest: the alleged second shooter, a 23-year-old black male, and the alleged driver of a getaway vehicle who had been shot in the incident. Craig said the alleged shooter had an outstanding warrant for his arrest for a felony charge in Virginia. At least one of the men has been involved in local gangs, he said.

A TEC-9 machine gun was recovered as part of the police investigation.

"[The shooting was] a decision made by a coward, once again, another coward that goes out and engages in senseless violence," Craig said. "We will continue our focus on eradicating violence, and certainly dismantling these street gangs here in Detroit."