By Todd Quinones

PHILADELPHIA (CBS)--Authorities say the shooter at the Paramus Mall had a history of drug dealing, drug abuse and was despondent.

Cell phone video captured the chaotic and terrifying moments after police say 20-year-old Richard Shoop began firing at least six shots at random inside the mall before killing himself.

“Out of nowhere, the guy walks past front door and is just shooting shots in the air,” eyewitness Clarice Forbes said.

Hundreds of frightened shoppers and employees were stuck inside as the mall went into lockdown.

Mall employee Carmen Reynolds says of the situation, “I always thought about it. Where would we hide if we had to hide? The place was always the bathroom.”

An employee tweeted a picture of herself to let loved ones know she was okay, as she huddled behind a clothing rack.

Kevin Shoop says his brother didn’t intend to harm anyone but himself on Monday night.

“He just sadly decided to make an act of, I guess self indulgence by taking his own life publicly,” Kevin Shoop said.

With the recent shootings at LAX and the D.C. Naval Yard, security expert and former New Jersey State Trooper Dennis Tully says it’s imperative people run, even scream, if they’re ever faced with a mass shooting scenario.

“Just do something; if you freeze you’re in trouble.  You could be in the crosshairs and get killed or hurt,” Tully said.

If running is not an option, barricading yourself in a locked room could also work, Tully says.

Above all, he contends now more than ever people have to take charge of their own security when going to a public location.

“Say to yourself, what would I do if x happened now or y happened now and play that scenario out in your mind real quickly,” Tully said.

No one other than the gunman was hurt in Monday’s mall shooting.

According to the research department at CBS News, dating back to the movie massacre in Colorado, 85 people have been killed in 11 mass shootings across the country in a little more than a year.

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