A top Iranian nuclear scientist, Mohsen Fakhrizadeh, was killed by five gunmen.
There have been successful assassinations of leading Iranian nuclear scientists since 2010.
This is the first successful assassination since 2012.
The Iranian government has difficulty recruiting scientists for nuclear research.
Arms Control Report on Iran’s Nuclear Program
The IAEA concluded that Iran’s uranium stockpile is now 12 times larger than permitted under the old nuclear agreement.