(CNN) In a private Instagram group chat, confessed school shooter Nikolas Cruz repeatedly espoused racist, homophobic and anti-Semitic views and displayed an obsession with violence and guns.

Wednesday, 19-year-old Cruz opened fire at the school that expelled him, Marjory Stoneman Douglas High School in Parkland, Florida. Authorities say he killed 17 with his legally purchased AR-15.

CNN, investigating comments the shooter may have left on a now-deleted YouTube channel, was added to the private Instagram group by one of the active members in it. The responding group members, who appear to be younger than 18, have refused to confirm their identities to CNN on or off the record.

When asked for comment or whether they knew about the private chat group, the FBI directed CNN to the Broward County Sheriff's Office.

Most of the conversation in the group since Cruz joined around August 2017 is between six people -- including Cruz.

"I hate jews, ni**ers, immigrants"

Racism was a constant theme in the chat group, which was called "Murica (American flag emoji) (eagle emoji) great" -- a name it was given by Cruz.

The hatred he and others in the group espoused met little resistance from its active members. In one part of the group chat, Cruz wrote that he hated, "jews, ni**ers, immigrants."

He talked about killing Mexicans, keeping black people in chains and cutting their necks.

There are hundreds of racist messages, racist memes and racist Instagram videos posted in the group.

One member even joked about Cruz's particular venomousness, saying that although he hated black people, too, he didn't "to a point I wanna kill the (sic) like nick."

Cruz said he hated black people simply because they were black; Cruz hated Jews because he believed they wanted to destroy the world.

After one member expressed hatred for gay people, Cruz agreed, saying, "Shoot them in the back of head."

White women drew Cruz's hatred as well, specifically those in interracial relationships, whom he referred to repeatedly as traitors.

There are no indications in the group chat that any member, including Cruz, is or was part of a white nationalist or white supremacist group.

Cruz used paycheck for body armor

Cruz purchased an AR-15 rifle in Florida approximately a year ago, legally. A law enforcement source told CNN's Evan Perez that Cruz purchased at least five guns in the past year.

In a public post on his Instagram page, Cruz showed what he called an "arsenal" on a bed -- seven guns and body armor. Another post on the page is a view down the barrel of a gun with a holographic sight out a window onto the street.

His AR-15 and other guns were a frequent topic of conversation in the group chat.

They even critiqued Cruz's rifle grip. He posted a short video of himself shooting a rifle outside a window at night. The video cuts out shortly after the round is fired.

A screenshot from a video showing Nikolas Cruz firing a gun out of a window.

They discussed which guns they liked better: M16s or AKs.

At one point, one member told Cruz, "Nick get this for your AR." He directed Nick to a website offering an after-market accessory that would turn his AR-15 into a fully automatic weapon.

A law enforcement source speaking to CNN's Evan Perez said that the gun used in the school shooting was not automatic, and there's no indication he bought the accessory, or a similar type of accessory.

When it was payday, Cruz let the group know where the money was going to be spent.

"Guys I got paid 330. I am buying body armor," he wrote.

Nikolas Cruz modeling his body armor.

Cruz did purchase the body armor, according to receipts he posted in the chat -- with a $30 discount and free shipping.

Then he asked the group whether it was legal to wear body armor to school.

"School shooters," he replied, when someone asked why he wanted to know.

"I think I am going to kill people"

The bio on one of his Instagram accounts read, "annihilator."

At one point in the chat, he wrote, "I think I am going to kill people." After a member told him not to say things like that, he said he was just playing.

During one of the anti-Semitic rants in the chat, Cruz spoke of his birth mother, saying, "My real mom was a Jew. I am glad I never met her."

Roger and Lynda Cruz adopted Cruz when he was a child. Roger died in 2004, and Lynda died last fall after an illness.

In his first message to the chat group, Cruz bragged about writing a letter to President Donald Trump -- and receiving a response. CNN reached out to the White House for comment about any correspondence to and from Cruz but has not heard back.

Jim Gard, his former math teacher, told CNN's Brian Todd that although he never had problems with Cruz, he did receive an email from a school administrator around November 2016 asking to be notified if Cruz came on campus with a backpack.

Nikolas Cruz's JROTC yearbook photo.

In two instances, Cruz also discussed killing small animals.

He posted a photo on his Instagram account of a disemboweled frog, saying he had killed it because one had killed his dog. In the Instagram chat, he describes killing a number of birds with his gun.

Some members of the chat were worried he might have killed endangered animals.

"He seemed nice but also had some mental issues," one member told CNN. "All (I know) is that he likes guns and really hates liberals."