This morning we held a special All School Assembly to address the horrific incidents at the marathon yesterday afternoon. Immediately following, students met in their advisories to discuss the tragedy. The following are my remarks to students and faculty:

Yesterday was an absolutely horrific day for Boston and the country.

Patriots Day is a joyously unique and quirky Boston day. The Red Sox play at 11 a.m. and the oldest marathon in the world takes place on a course like no other mid-morning on a Monday, rather than early on a Sunday like all other marathons.

No one calls it the Boston Marathon. It’s The Marathon.

After the Sox game fans pour out of Fenway to cheer on the runners. The city shuts down for what feels like Boston’s first day of spring. No other city in America has a day like it.

And then at 2:50 everything changed.

Thousands watched in horror — and millions have watched online and on television — as two bombs exploded at the finish line. Suddenly it didn’t feel like spring.

We are still learning about what happened and we have not begun to learn the who or why. We know that 3 have died, that at least 130 were injured, and at latest report, 30 of those have life threatening injuries.

As far as we know everyone in our Beaver community is safe, but we know that there are people in this room who were there yesterday and who know people directly affected by yesterday’s events.

Today is a day to mourn, to ask questions, but not to speculate. It is a time to be grateful for all those who acted selflessly and heroically in the moments following the blasts:

Spectators in shock with ears ringing and exhausted runners immediately rushing toward the explosions to assist the injured, many very seriously injured.

The Boston Athletic Association, the group that organizes the marathon, responding instantly to shut down a huge event to ensure safety and allow medical personnel, police, the National Guard and the FBI to do their jobs.

Boston Police, who as soon as they heard the first blast, drew their weapons, and ran toward the scene.

Officials who locked down an enormous event — even to the point of shutting down cell service — and made sure everyone got out of Copley in as safe and orderly way as possible.

The responses from Mayor Menino, who left his hospital bed, to Gov. Patrick, to President Obama.

The reaction from around the country. I would guess everyone in this room received a text or a Facebook message or a phone call from someone out of town asking if everything was OK.

And finally, all the medical personnel in the finish line medical tent. Most of these nurses, including our school nurse Sarah Chorney, and doctors volunteer, many for years, to support the Marathon. On any other marathon day they treat runners with blisters and hypothermia. In a moment, they had to pivot and become a battlefield triage unit. I can’t begin to imagine what yesterday was like for them, but they were extraordinary and doubtless saved lives.

Here we are, 19 hours later, left with profound sadness, lots of questions, and no answers.What we do know is that on this uniquely Boston day the people of Boston, officials, and anonymous citizens, stepped up and responded in a typically Boston way.

All of us are thankful for them.