Ten people were shot and at least 29 hurt Tuesday morning when a masked gunman opened fire on a Brooklyn subway train and then on the platform during morning rush hour.

The attack stunned the region. News 12 spoke with Sal Lifrieri, president of the security firm Protective Countermeasures, about how to respond if you are in a similar situation.

MORE: 8 safety tips for traveling in the subway and railroad

His main advice: Be aware of your surroundings.

“Put the phone away. Take the earbuds out. Know what’s going on. Be able to hear and listen to what’s going on,” he said.

He added that if you hear something or see something that’s suspicious, “then say something.”

Lifreiri says the attack on the subway serves as a reminder to protect against misinformation.

"Listen to your actual local law enforcement community or political leadership when they're telling you about breaking news and giving you updates to what they know," he said.

Check out News 12’s live blog for the latest information on the subway shooting.