Last Saturday burned hot and beautiful in Berlin. I woke up late and joined hundreds of thousands of people marching through the city for Christopher Street Day, our biggest Pride event. Several Pride events happened that weekend, but I went to the big one because my boyfriend worked a shift that day at a shop in Schöneberg, Berlin’s classic gayborhood, near the start of the parade route, and I wanted to spend this holiest of days with him.When he got off work, we finally joined the throng, a bit too late, well behind our friends and lovers who had followed the route all day to the Tiergarten, the large park where the parade ends in front of the Brandenburg Gate and becomes a street party so full of people that it becomes hard to move. That’s where, just before 10 p.m., a man drove a van into the crowd.Related: Terrorist attack at huge Berlin Pride parade celebration leaves 1 dead, dozens injuredPer the German newspaper Tagesspiegel, the van entered the park and struck people leaving the finale before colliding with a tree; the driver continued on foot with a machete, the Associated Press reported. One friend said the van blew past him so close that he saw the driver's face through the window and described it as blank, unfeeling, determined. The man killed one woman, a 65-year-old Polish citizen, who was visiting Berlin with her daughter, and wounded 29 more, some severely. Thankfully, no one I knew was hurt, and I was not hurt, but still, it brought a painful, abrupt end to a day of joy and love.How did a known subject carry out a deadly terrorist attack?How did it happen? The attack took place in one of the most heavily policed parts of the city, a short walk from the Bundestag, the seat of the German government. After a daylong manhunt, officers shot and killed the attacker, 21-year-old Abdul Ballout. Ballout had attempted to join the Islamic State, the jihadist terror group, in Syria, and authorities ruled it a terrorist attack.Being attacked and experienci