BOSTON (WWLP) – It has been exactly nine years since three people were killed and more than 260 wounded at the Boston Marathon.

On April 15, 2013, the City of Boston came under attack, when terrorists planted two-homemade bombs near the finish line of the marathon.

The incident was witnessed by thousands, those who were passing by helped the wounded, and many lives were changed forever.

Friday, the city of Boston will celebrate “One Boston Day” to honor the resiliency, generosity, and strength demonstrated by the people of Boston back on April 15, 2013.

Monday is the second Boston Marathon in six months and the city is expecting upwards of 30,000 runners at the start line in Hopkinton and close to 500,000 spectators along the course. On everybody’s mind is public safety. Boston Mayor Michelle Wu announced that there will be uniformed and undercover officers all along the route. Boston Fire and Boston EMS will also be patrolling the 26.2 mile course to help anyone in need.

As for COVID-19 precautions, all athletes must be fully vaccinated to compete and Wu’s office is encouraging onlookers to be vaccinated, to have recently tested negative for COVID-19 or to wear a mask while cheering from the sidelines.