A 72-year-old man died by suicide after he allegedly killed 11 people in a mass shooting at a?Monterey Park, California, dance studio on Saturday night. Two days later, a 67-year-old man was taken into custody for allegedly gunning down seven people in Half Moon Bay, California.
It's rare to see mass shooters in their 60s or 70s, experts say.
Out of the?61 active shooter incidents in 2021, just six shooters were between 55 and 64 years old and only one shooter was 65 or older, according to the FBI. Eighteen shooters were between 25 and 34 years old and 14 shooters were between 19 and 24 years old, according to the FBI.
"Isolation, anger, rage, revenge and feeling completely powerless. Whether you're 12 years old or 72 years old, that still is sort of the hallmark of what mass shooters are," former FBI agent and ABC News contributor Brad Garrett said.
But Garrett said this week's mass shootings tell "those of us who study this every day that you can't get too locked in because you're talking about human behavior." With "human behavior, there is no black and white -- there's a lot of gray," he said, based on ethnicity, religion, geography and more.
So who are these older shooters and why are they so rare?
In this week's shootings, the suspects were older Asian men who targeted Asian victims in their own communities, Garrett noted.
The motive is unknown for 72-year-old Huu Can Tran, the Monterey Park suspect. He is accused of opening fire on Asian victims his own age at a dance hall where he'd spent time before.
Tran’s former tenant and longtime acquaintance told ABC News that Tran spent his nights mainly alone but would offer women free lessons in the dance studio. The acquaintance, who did not want to be named, said Tran "just couldn't get along well with people."
For the Half Moon Bay shooting suspect, 67-year-old Chunli Zhao, workplace violence was believed to be the motive, according to authorities. Zhao allegedly opened fire at two farms, including a farm where he worked. The victims were adults of Hispanic and Asian descent, authorities said.
Men are usually more violent when they're younger and it can take until their mid-to-late 20s for their brains to develop enough to have sufficient impulse control, Garrett said.
A young man "is really only thinking about revenge," he said. "He's not thinking about the effects of what he's going to do on other people."
For older suspects, baggage can be a factor, Garrett noted.
"The thing about being older is you've also collected more baggage, as we all do in life, because of relationships, because of job failures, because of marriage failures, whatever it might be. And that can really build up as you get older," Garrett said.
Mental health may also be a component for this week's shooting suspects, Garrett said.
According to Garrett, the only way to stop mass shootings is to know about them ahead of time. Sometimes police get information on school shootings or workplace shootings before they happen.
"Firearms are just so readily available," Garrett said, noting that guns are purchased legally in most mass shootings.
Zhao, the Half Moon Bay suspect, was not known to police, authorities said. His semi-automatic handgun was legally purchased and owned, authorities said.
Tran, the Monterey Park suspect, had minimal criminal history. Authorities said he was arrested in 1990 for unlawful possession of a firearm, according to officials.
At Tran's home authorities said they recovered a .308 caliber rifle, homemade firearm suppressors and hundreds of rounds of ammunition in containers. Tran had a semi-automatic assault weapon with him Saturday night when he entered a second dance hall and was disarmed by a good Samaritan. Investigators also recovered a handgun in the van where Tran died by suicide.
Zhao made his first court appearance on Wednesday. He has not yet entered a plea.