Since this word has okurigana (hiragana attached to the kanji) you know that it's probably going to be the kun'yomi reading.
Lucky for you, the kanji readings for transitive and intransitive verbs are almost always the same. Once you learn one, you know them both! This reading is the same as 砕く.
Suddenly, the window shattered into tiny pieces.
I like sitting on the beach and watching the waves break on the shore..
When I felt like the tension in the air finally broke, the party was almost over.