DENVER (CBS4) – Denver police on Wednesday say they have arrested a juvenile male in a shooting that left a student critically injured outside DSST: Cole Middle School. He was arrested overnight and is being held for investigation of aggravated assault.

The gunfire rang out on Tuesday just before 2 p.m., only a week into the school year. The school is located near the intersection of M.L.K. Jr. Boulevard and Downing Street in the city’s Cole neighborhood.

A student who was in the school told CBS4 she heard shots outside the classroom.

“All of a sudden we heard maybe seven gunshots go off and then we heard the loudspeaker saying we were on lockdown and hide,” she said.

“We have windows all around our classroom so we hid against the wall,” another student said.

Many parents expressed frustrations with school officials for not alerting them right away about the shooting. Some didn’t know the school was on lockdown until they saw it on Facebook.

Stormey Ware says she never received a notification about the lockdown and only learned it from her oldest daughter who was in a nearby building.

“I don’t want to hear it from my other daughter calling me, or from Facebook or somewhere else okay? We are the parents. You guys are supposed to protect them while they’re here,” she yelled while pointing at the school.

Her frustration was echoed by several other parents, including Maryjane Henson who was there trying to pick up her grandson.

“It was kind of scary being told they were on lockdown, but not know why,” she said. “And then saying they are going to be let loose, and then they are not for another 45 minutes, then it makes you really anxious and nervous.”

Officials from Denver Public Schools will meet on Tuesday will discuss how they could have better handled the situation. Spokesman Will Jones said the school was immediately put on a lockout, but they do not notify parents for a lockout. He says it should have been a lockdown — at which time parents would have been notified right away.

Last week CBS4 covered new procedures for school security and safety at all DPS schools. One of those procedures includes how schools perform lockdown drills.

Students will be provided with counseling at the school on Wednesday. There will also be heightened security on the campus, even after the announcement of an arrest in the case.

So far it’s not clear what led up to the shooting, and when asked on Tuesday about the possibility of a gang being involved, Denver Police Chief Paul Pazen said it was too early in the investigation but that investigators will “look at all possible angles.”

The shooting victim is still in the hospital and fighting for his life.

Albus Brooks, a Denver city councilman, wrote in a Facebook post that police told him two 13 year olds were involved in the shooting.

Denver Public Schools acknowledged their response could have been better to Tuesday’s shooting. The district responded on Wednesday to the frustration many parents expressed when picking up their students.

“Yesterday was a tragic event, anytime we have a situation with a school shooting near one of our schools, it’s definitely concerning for us,” said Chief Michael Eaton, with the department of safety for the school district. “The safety of all our students is our first priority.”

Eaton explained that they have protocols to follow for this type of situation but says improvements need to made by the department. He said there was a delay in providing information but the process requires them to work with Denver Police whenever there is a criminal investigation.

“We are battling the age of social media, of texting, things being immediate,” Eaton added.

Parents were getting messages from their children or seeing posts on Facebook before they received notifications from the school district. Eaton says they cannot eliminate the challenge that comes with students sharing information before they do. Eaton says the district wants to apologize for the frustration families felt on Tuesday and that they will review the procedures in place based on the response outside of DSST: Cole Middle School.

“We can do better in our communication protocols,” he said. “We’re going to identify where those gaps are, and we’re going to make those corrections immediately.”