Sunday afternoon's attack in Boulder, Colorado, took place hours before the start of a major Jewish festival, Shavuot.
Authorities say a man threw two incendiary devices into a group holding one of its regular rallies in solidarity with Israeli hostages in Gaza. Twelve people were injured and the FBI described the violence as a ''targeted terror attack.''
What is Shavuot?
Shavuot (pronounced Shah-voo-OTE), Hebrew for ''weeks," has been observed since biblical times. It marks the passing of seven weeks (49 days) from the holiday of Passover, with Shavuot falling on the 50th day.
In biblical times, Shavuot was an agricultural festival, when Israelites would bring harvest offerings to the temple.
Today, it's primarily commemorated as the traditional date on which God gave the Torah — the law that forms the heart of the Jewish Scriptures — to Moses on Mount Sinai, as described in the Bible.
The 50-day time period gives the festival its Greek name, Pentecost, which is also the name for a holy day on the Christian calendar.
When is Shavuot?