The gunman in the deadly rampage in Dayton, Ohio, was wearing a mask, bulletproof vest, earplugs and was carrying a rifle capable of holding at least 100 rounds when he opened fire outside a bar, killed nine - including his sister - and injured more than two dozen, one in critical condition, police said Sunday.

Dayton police Chief Richard Biehl told reporters in a news conference on Sunday afternoon that the gunman, identified as 24-year-old Connor Betts, showed up to the city's Oregon District around Fifth Street with his sister and a friend on Saturday night. He added the three separated at some point between when they arrived and when Betts opened fire, saying it is unknown what happened during that time.

Biehl said police officers in the area engaged him seconds after the first gunshots were heard and the gunman was "neutralized" within 30 seconds after the first of "dozens of rounds." Betts was shot and killed by police before he entered Ned Peppers Bar. He was using a .223-caliber rifle.

"At 1:05 a.m. officers were patrolling the Oregon District during bar closing time and heard gunfire. They observed a large crowd running away from this gunfire," Biehl told reporters.

"The officer's immediately advance toward the gunfire and within approximately 20 seconds, they engaged the suspect who was actively firing and attempting to enter a crowded liquor establishment. The threat was neutralized in approximately 30 seconds of the suspect firing his first shot."

Biehl added that had Betts gotten inside, the result would have been “catastrophic.”

“There’s nothing in this individual’s history or record that would have precluded him from purchasing that firearm,” Biehl said.

Biehl told reporters Betts had two guns with him, adding that a shotgun was left in the vehicle at the time of the shooting.

The shooting came fewer than 24 hours after at least 20 people were killed at a Walmart in El Paso, Texas.

Police confirmed early Sunday that Betts' 22-year-old sister Megan Betts, was among the nine killed. Biehl said Betts' sister was not the first person killed but among the initial victims. She was with a companion, who was injured in the attack.

He said investigators have had a chance to speak with the friend, but did not disclose what was discussed, saying the investigation is ongoing.

When asked if Betts’ sister and the friend were targeted Biehl told reporters investigators could not tell at this point, adding that it is a "nagging question."

He said, “We're trying to sort through that ourselves.”

Biehl told reporters one sergeant and five officers fired at least one shot and have been placed on administrative leave, which is standard procedure. He said it is too soon in the investigation to determine a motive and would not disclose what evidence has been gathered.

“We have a lot of evidence to process through," Biehl said.

"This is a heartbreaking tragedy," Ohio Gov. Mike DeWine told reporters at a news conference Sunday afternoon. "It is the type of tragedy that you hope never comes to your state."

DAYTON, OHIO, SHOOTING THAT LEFT 9 DEAD, 27 HURT HALTED 'IN UNDER A MINUTE' BY COPS WHO SHOT SUSPECT: MAYOR

The other victims were identified as 27-year-old Lois L. Oglesby, 38-year-old Saeed Saleh, 57-year-old Derrick R. Fudge, 30-year-old Logan M. Turner, 25-year-old Nicholas P. Cumer, 25-year-old Thomas J. McNichols, 36-year-old Beatrice N. Warren-Curtis and 39-year-old Monica E. Brickhouse.

Dayton Mayor Nan Whaley said the Oregon District was filled with "thousands" of people out on a weekend night at the time and that officers were also stationed in the neighborhood before the shooting began.

“If Dayton police had not gotten to the shooter in under a minute ... hundreds of people in the Oregon District could be dead today," Whaley told reporters.

DeWine praised the fast response by law enforcement, saying it saved "many, many lives" and the assailant was "very close" to killing "dozens and dozens more people."

"In this tragedy, we have to thank our first responders," the governor said.

Officials said there will be a vigil at 8 p.m. on Sunday in the Oregon District to remember the victims of the shooting.

Whaley said at least 27 people were treated for injuries, and at least 15 of those have been released. Several more remain in serious or critical condition, local hospital officials said at a news conference Sunday.

EL PASO SHOOTING SUSPECT CHARGED WITH CAPITAL MURDER; MASSACRE BEING INVESTIGATED AS DOMESTIC TERRORISM

The Oregon District is a historic neighborhood that was described by officials as "a safe part of downtown," home to entertainment options, including bars, restaurants, and theaters.

Abandoned shoes were seen in the area of the shooting -- left behind as panicking people fled. Police tape could be seen on Sunday morning near a pile of shoes outside the bar where the gunfire erupted.

Whaley told reporters on Sunday afternoon that the Oregon District had been reopened.

Authorities descended on a neighborhood in Bellbrook, located about 16 miles south of the shooting scene, as they executed a search warrant in connection to the deadly shooting, WKEF/WRGT reported. Bellbrook Police Chief Doug Doherty told the television station the search was to "obtain information tied to the shooting in Dayton."

Doherty said he and his officers weren’t aware of any history of violence by Betts, including during high school, The Associated Press reported.

During Sunday afternoon's news conference when asked if Betts was known to police Biehl answered, “not at all.”

President Trump ordered flags at half-staff in remembrance of the victims of two mass shootings in less than a day. He denounced the two mass shootings when addressing reporters in Morristown, N.J., saying "hate has no place in our country."

Trump told reporters that "we're going to take care" of the problem. He said he had been speaking to the attorney general, FBI director and members of Congress and will be making an additional statement Monday morning.

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Trump pointed to a mental illness problem in the U.S., calling the shooters "really very seriously mentally ill."

Fox News' Gregg Re and The Associated Press contributed to this report.