(CNN) During the weekend in Chicago, 66 people were shot, 12 of them fatally, between Friday at 6 p.m. and Sunday at 11:59 p.m.

"It's no secret that we had an unacceptably violent weekend," Police Superintendent Eddie T. Johnson said.

The spate of shootings left Chicago officials visibly frustrated during a Monday press conference, in which they said gun offenders needed to be held accountable, and they pressed for more community cooperation to stem the crimes.

In all, over the weekend, there were 33 shooting incidents. Fourteen juveniles were shot, and two 17-year-olds were killed.

In at least one incident, shooters opened fire into a crowded street party, police said. Of the wounded who reported an age, the oldest was 62 and the youngest 13, police records show.

Johnson said 46 people were arrested this weekend on gun charges, and 60 guns were seized as a result of ongoing investigations. However, he said there have been no arrests made in connection with any violence from this weekend.

"Somebody knows who did it. They do. They know that," the police superintendent said. "They hold me accountable. They hold the mayor accountable. They hold the city council accountable. Where's the accountability?"

"I never hear people saying, 'These individuals out here in the streets need to stop pulling the trigger.' I never hear that. They get a pass from everybody."

He urged people who know something to come forward.

"These shootings are not random, they're fueled by gang conflicts. We know who they are and we continue to send a message that it's OK to commit these crimes by not doing anything as a community. We are all supposed to be on the same side. CPD can be better, but this city can be better," Johnson said.

Chicago Mayor Rahm Emanuel also called on community members.

"We as a city, in every corner, have an accountability and a responsibility. If you know who did this, be a neighbor, speak up," Emanuel said.

Experts say crime tends to pick up during the hot summer months, but Emanuel dismissed that.

Officers investigate a shooting in Chicago on Sunday.

"You can talk about the weather, but the weather didn't pull the trigger," he said. "You can talk about jobs, and they count, but in parts of the city where there aren't jobs, people did not pull the trigger.

"There are values. There are too many guns on the street, too many people with criminal records on the street, and there is a shortage of values about what is right and what is wrong," he added.

Emanuel said there's something more at stake.

"All of us know that this is not Chicago -- what we saw," he said about the violence over the weekend. "Therefore, all of us who love this city and call it home have a responsibility to heal our neighborhoods."

In three hours beginning at 1:30 a.m. Sunday, records show, 30 people were shot and two killed in 10 incidents.

"The city of Chicago experienced a violent night," Bureau of Patrol Chief Fred Waller said Sunday afternoon. "Some of these instances were targeted and were related to gang conflicts in those areas."

Before the particularly violent Sunday, there were six shootings, none fatal, on Friday, and 15 shootings, one fatal, on Saturday.

Chicago has struggled with high shooting and murder rates in recent years. Waller said shootings are down 30% from 2017, and murders are down 25%.

June marked 15 straight months of fewer killings and shootings, police said. However, on June 25, at least 21 were shot and two died.

Johnson said that both murders and shootings are down on the year, but said this weekend showed there was still a lot to do.

"Despite what we saw this weekend, I'm still pleased between CPD's work, the mayor's investments, and the work of our community members, that we're still reducing our gun violence this year," Johnson said. "But we still have a lot more work to do, and I think that was evidenced by this weekend."

CORRECTION: This story has been updated to correct the ages provided by Chicago police on the juvenile victims of the weekend violence.