Last night seven people were killed in what the Metropolitan Police have described as a terrorist attack at London Bridge and Borough Market.
Some 48 people are being treated in hospitals following the attack, which the police say they responded to and stopped within 8 minutes.
Three attackers were shot dead at the scene.
When a terrorist attack is recent, there's a tendency for social media to inflate misinformation as people share details unchecked.
There's still many details yet to be confirmed by authorities about the attack.
Here's a brief guide to how to behave responsibly on social media at a time like this:
1. Get your news from official sources.
There have been incidents of people sharing false images claiming they are identifying attackers or victims.
You should receive details from official sources - by which we mean the relevant emergency services such as the Metropolitan Police, and statements from government figures such as the Prime Minister and the Home Secretary.
Don't believe all you read online.
Check your information is also confirmed by authorities, and if it's unconfirmed, just don't tweet it.
2. If you think you have information, send it through the right source before spreading it on social media.