Two overnight shootings, including one in which four police officers returned fire, punctuated a weekend of gun violence as South by Southwest festivities drew to a close in downtown Austin, prompting Police Chief Brian Manley to pledge more security for the city's entertainment district.

It was the second consecutive night that officers were called to multiple shootings. In the wee hours of Saturday morning, three separate shootings across the city, all occurring within a four-hour span, sent five people to the hospital with three of them seriously injured, authorities said.

Within 24 hours, two more shootings occurred. Austin-Travis County Emergency Medical Services medics responded just before midnight to a shooting in the 300 block of East Sixth Street. They took a man thought to be in his 20s to a hospital for a gunshot wound at 11:58 p.m.

Austin police said via Twitter that "individuals have been detained" in the shooting, but investigators were still searching for others who might have been involved.

About 2:50 a.m. Sunday, officers responded to another shooting at the Interstate 35 North frontage road and Seventh Street, and they traded gunfire with an unidentified man at the intersection, police said. By Sunday afternoon, police in the Mueller neighborhood in East Austin had found the body of a man in a vehicle that was involved in the shooting.

"This comes on the heels of what has been a violent weekend in Austin, where we have seen multiple shootings," Manley said. "And this is unacceptable. We are not going to let our entertainment district be turned into a place where shootings become the common occurrence."

The chief said he would meet with Police Department leaders and others this week to "put together a plan to ensure that we have additional officers in the entertainment district so that we can maintain the level of security, so that people can come downtown, enjoy their time and do so safely."

After viewing video taken from HALO surveillance cameras, police think the shooting on Seventh Street was triggered by a minor collision between a Maserati Levante and a Chevrolet Monte Carlo at Neches and Seventh streets. The vehicles then headed east to the intersection of Seventh and I-35 and stopped at a traffic light. There, two men got out of the Levante and went to the driver's side of the Monte Carlo, where one of the men punched someone inside the car, Manley said.

HALO video then shows a muzzle flash from inside the Monte Carlo and one of the attackers doubling over, indicating that one of the car's occupants fired a weapon at the attacker, Manley said.

Officers arrived, Manley said, and saw the wounded man draw a pistol from his waistband. The man, who was returning to the Levante, then fired at police, and four officers returned fire, the chief said. Both the Levante and the Monte Carlo drove off, and police are still looking for the vehicles and their occupants.

A third car at the intersection during the encounter had been struck by gunfire and was later flagged down by officers at 11th Street and I-35. According to video footage and witness accounts, the car tried to get away as the shooting started, but as it passed the Levante, a man in the third car was wounded, Manley said. He said the man's injuries were serious but not life-threatening.

At 5 p.m., police announced they had found the Levante in the Mueller neighborhood in East Austin. But officers also found the body of a man in his 20s who matched the description of one of the men involved in the Seventh Street shooting. Police said they had not yet positively identified the body and declined to provide any other details.

Investigators continued to search for the other vehicle in the shooting, a dark-colored Monte Carlo with white racing stripes on its hood and damage on its right front quarter panel. Authorities said sightings of either vehicle or any other information related to the case should be reported to 911 or the Austin police homicide tip line at 512-472-8477.

Manley said none of the shootings appear to be related, and police did not know whether the men in the vehicles were from Austin or visiting during SXSW.

Of the four officers who returned fire, two have been with the Police Department for seven years, one is a 12-year veteran and one has been on the force for three years. The officers, who were not identified Sunday, will be on administrative duty as internal and criminal investigations are conducted, which is standard protocol in all Austin police shootings.

"I want to point out here that as a result of the shooting that occurred last night, we had shifted our resources and we had approximately 50 officers working this intersection between Sixth Street and Seventh Street, both the east frontage and the west frontage, in the parking lot of the gas stations, of the Wendy's restaurant, again in response to what happened last night," Manley said.

"And what you can see on this video is that as this gunfire rings out, and this dangerous situation plays out, as everyone is running away, the brave men and women of the Austin Police Department ran towards that gunfire, in fact putting themselves directly in the line of fire in an attempt to put a stop to this threat," he said.