(NECN: Kathryn Sotnik) - For Lt. Jeremy Walsh and his fellow Cambridge, Mass. firefighters and paramedics, April 15, 2013 started like every other day.
It was routine. Lt. Walsh was on duty at the time, out on the road in Squad 2 with another paramedic when in the late afternoon, he received word of the bombings.
"Somebody had said something about explosions at the finish line," he said.
That's when his life forever changed. An alert was put out for all ambulances to respond to the Boston Marathon finish line. The time was around 3 p.m. Lt. Walsh responded to the second bombing in the area of the Forum restaurant.
The task at hand was to look for anyone who was hurt and treat them.
"There were several patients who had shrapnel injuries," said Lt. Walsh. "A lot of walking wounded, and we were just looking to assist in any we that we could."
A possibility that he could also get hurt was in the back of his head.
"Coming over here, I knew that there was a second bombing, I knew that was some distance from the first one. We know that's what terrorists, or whoever, like to do. They like to sometimes set up multiple explosions so that they can get people who are running away," he said.
In the dark seconds after, he contacted his wife and daughters to let them know he was OK.
"The runners were gone, the spectators were gone, I texted my wife from down here just to say I am here," said Lt. Walsh.
Now, looking back, Lt. Walsh says he can't believe a year has passed.
"It's on your mind almost every day, the stuff that happened that week," he said. "In training, it's always been, it could happen, it might happen, it's going to happen. But you always think, 'could it happen here?' But I guess, deep down, I never expected it to."
But unfortunately, it wasn't over just yet. Lt. Walsh says the most challenging time for him was the tense and tiring days that followed.
On the Thursday after the bombings, he was stationed outside Brigham and Women's and Children's Hospital while First Lady Michelle Obama visited the victims.
When he got back to the Cambridge Firehouse, the FBI had released the photos of the bombing suspects.
Next, 26-year-old Sean Collier, an MIT police officer, was gunned down in his cruiser in Cambridge, allegedly at bombing suspects hands.
Lt. Walsh was one of the first paramedics to treat Collier at the scene and was in charge of the response.
"I've never had another police officer shot, and just to see the looks on other police officers' faces, MIT and Cambridge who were both there, that was tough," he said.
With a heavy heart, Lt. Walsh had to continue on.
He's also a tactical medic with the Cambridge Special Response team, so he responded to Laurel Street in Watertown following the gun battle where Suspect Number One, Tamerlan Tsarnaev, was killed.
For 18 hours, the search for Suspect Number Two, Dzhokhar Tsarnaev, was on.
Looking back at the events of that week, Lt. Walsh says he doesn't do anything differently. He just feels a little more grateful.
"Absolutely thankful for every day," he said. "A lot of people were injured and lost their lives. You hug your kids and wife a little tighter that night."
That week will forever be in his mind.
"It doesn't go away," he said. "Maybe someday."
Lt. Walsh feels it's important to reflect on the memories of that day. He was one of many first responders who took part in a special seminar in Boston called "Our Marathon: Stories from the Scene."