A police officer stands at a police cordon near the scene of a terror attack in London, U.K., on Sunday, June 4, 2017. A van swerved into Saturday-night crowds on London Bridge, before three men got out and went on a stabbing rampage through nearby bars. (Photo by Luke MacGregor/Bloomberg)

A young boy plugs his ears as his sister (C) and nanny (L) watch from Gravelly Point Park as planes land at Reagan National Airport in Arlington, Virginia on June 29, 2017. President Donald Trump' s travel ban on people from six mostly Muslim countries will come into force late Thursday, as controversy swirls over who qualifies for an exemption based on family ties. (Photo by Jim Watson/AFP Photo)

A bonnet macaque sits on consecrated idols of snakes as it drinks milk offered by a devotee during the Hindu festival of Nag Panchami, which is celebrated by worshipping snakes to honour the serpent god, inside a temple on the outskirts of Bengaluru, India, July 27, 2017. (Photo by Abhishek N. Chinnappa/Reuters)

Londoners enjoy a “Silent Night” as Big Ben falls silent, London, UK on August 21, 2017. ose Allerston from Clapham, London said “After a stressful day in the office, I couldn't think of anything better than going home and climbing into bed – but when I saw this bed opposite Big Ben I just couldn't resist getting in for a snuggle”. (Photo by Imagewise Ltd/Rex Features/Shutterstock)

A drunk student is sick on the street watched by a police officer following a night of heavy drinking during freshers week in United Kingdom on November 28, 2007. (Photo by Matthew Horwood/Alamy Stock Photo)

Charles Manson plays up to the camera during a 1988 interview with reporter Geraldo Rivera at San Quentin prison in 1988. Authorities say Manson, cult leader and mastermind behind 1969 deaths of actress Sharon Tate and several others, died on Sunday, November 19, 2017. He was 83. (Photo by AP Photo)

Giving out with a yell, Elke Sommer is tossed on the trampoline as she trains for her movie role as an athlete, on the playing field of the University of California at Los Angeles, June 8, 1967. (Photo by AP Photo)

A U.S. Army crew chief flying on board a CH-47F Chinook helicopter observes the successful test of flares during a training flight in Afghanistan, March 14, 2018. (Photo by Tech. Sgt. Gregory Brook/Reuters/U.S. Air Force)