On December 1, 2015, Zuckerberg and Chan announced the birth of their first daughter Max, and in an open letter to Max, they pledged to donate 99% of their Facebook shares, then valued at US$45 billion, to the Chan Zuckerberg Initiative, their new organization that will focus on health and education.
On December 2, 2015, 14 people were killed and 22 others were seriously injured in an Islamic terrorist attack consisting of a mass shooting and an attempted bombing at the Inland Regional Center in San Bernardino, California. The perpetrators, Syed Rizwan Farook and Tashfeen Malik, a married couple living in the city of Redlands, targeted a San Bernardino County Department of Public Health training event and Christmas party of about 80 employees in a rented banquet room. Farook was a U.S.-born citizen of Pakistani descent, who worked as a health department employee. Malik was a Pakistani-born green card holder.
Musk believed the key to making space travel affordable was to make rockets reusable, though space industry experts believed reusable rockets were impossible or infeasible. On December 22, 2015, SpaceX successfully landed the first stage of its Falcon rocket back at the launch pad, the first time this had been achieved by an orbital rocket.