ST. PAUL -- I spent about four hours covering an anti-poverty protest Tuesday night outside the Republican National Convention in St. Paul. Four hours of a peaceful protest turned violent in a matter of seconds. (Police Use Pyro To Break Up RNC Protests)

The afternoon’s event started with a rally in St. Paul’s Rice Park, a small one-block park tucked among the office and apartment buildings downtown.

Other than a minor skirmish with police that happened far from the main stage, the protest was largely peaceful.

That’s amazing considering that the crowd of anti-poverty protesters grew as the parade wound a twisted route from downtown St. Paul to the Capitol and then back to the downtown’s Xcel Energy Center. That is where the RNC was gathered listening to Laura Bush, Joe Lieberman and Fred Thompson.

It was a tense time as more than 2,000 protesters walked toward a solidly fenced barricade separating them from the Xcel Energy Center. I walked a few yards ahead of the crowd and kept wondering just how out of control this protest may get.

The actual protest never did get out of control. Volunteers raised the protest leader above their heads. She asked everyone attending to raise their right hand and pledge for a peaceful end to their march. (Protesters Take Peaceful March To RNC Gates)

The trouble with this protest happened as the crowd started to walk away from Xcel Center. They encountered a barricade of police, standing arm to arm, ready to maintain crowd control.

This seemed to inflame some protestors who often taunted police at the end of the march.

I started to heed a police warning to leave the area when I noticed several protestors overtly challenging police. They videotaped the police who videotaped them. They edged closer and closer to the chain of police in riot gear.

I knew the protest pot was ready to boil over.

I positioned myself on a far end of the human police barricade. I had a great camera angle to see protesters on the right of my frame and police standing firm on the left.

I heard one protestor say to another, "See, they’re giving the order."

Seconds later, a boom rocked the crowd. Some protesters started to surge toward the sound until they realized it was a smoke bomb. Flash grenades and what smelled like tear gas followed. It sent protestors running. The smell was overwhelming. Cries of people needing water to wash their eyes could be heard.

For the second consecutive day, St. Paul’s downtown was brought to a crawl because of protests.