A mystery pianist set up a piano outside of Paris' Bataclan concert venue Saturday, following a terrorist attack Friday night that left  129 people dead (so far) and nearly 400 injured.

As people gathered to mourn and pay their respects outside Bataclan, the man pulled up, towing his piano behind his bike, and set up. He then sat and played a completely instrumental version of John Lennon's classic "Imagine". 

A small crowd quickly formed around the man as he played, with many on-lookers taking photos and videos of the performance.

Flowers, candles and memorials were also set up outside the Bataclan, the concert hall that was the epicenter of Friday's attack. The attack made Friday the deadliest single day in France since World War II.

France has declared three days of mourning following the attacks.