Here are some things to know about yesterday's attack:
1. On September 15th during Friday morning rush hour, a bucket bomb was detonated on a packed subway train at Parsons Green station in London.
2. The blast injured many, sending 29 people to the hospital.
3. Fortunately, the police said the improvised explosive device used did not fully explode.
4. A timer on the bomb was found, suggesting major damage was intended.
5. The device was a white plastic bucket with wires protruding from it with flames.
6. An ISIS affiliate has taken responsibility for the attack.
7. Only hours after the attack, officials in the United Kingdom raised the terror threat to the highest possible.
8. Police have arrested an 18-year-old man in connection to this attack in the Dover area.