Bette Midler,The Big Sick star Zoe Kazan, This Is Us star Mandy Moore and Ben Stiller are among those in Hollywood speaking out after a gunman opened fire at a Pittsburgh synagogue Saturday.

"No one should have to go through airport security to go to pray in a synagogue or church or a mosque," Meet The Parents star Ben Stiller wrote Saturday, adding the hashtag #guncontrol.

No one should have to go through airport security to go to pray in a synagogue or church or a mosque. This is not the fault of the synagogue....<a href="https://twitter.com/hashtag/Guncontrol?src=hash&ref_src=twsrc%5Etfw">#Guncontrol</a> <a href="https://t.co/WiIYqSla3s">https://t.co/WiIYqSla3s</a> —@RedHourBen

Stiller was one of many celebrities making reference to the heated debate in the U.S. over gun law reform.

"My heart goes out to all those affected by gun violence today and every day," Mandy Moore wrote on Twitter. "Feeling helpless and frustrated by this news too? Vote Nov 6th. Vote. Use your voice."

My heart goes out to all those affected by gun violence today and every day. Feeling helpless and frustrated by this news too? VOTE Nov 6th. VOTE. Use your voice. <a href="https://twitter.com/hashtag/GunSenseCandidates?src=hash&ref_src=twsrc%5Etfw">#GunSenseCandidates</a> <a href="https://t.co/LCi3ufyMJH">https://t.co/LCi3ufyMJH</a> —@TheMandyMoore

Moore wasn't the only one whose message about the mass shooting also included encouragement to vote in the upcoming American midterm elections, which could see changes to the Republican-majority Congress.

"The guns are the long arm of this racist, sexist, anti-Semitic, anti-LGBT administration," Kazan posted Saturday. "The laws and judges being put in place are the longest arm. Vote. Them. Out."

the guns are the long arm of this racist, sexist, anti-Semitic, anti-LGBT administration. the laws & judges being put in place are the longest arm. vote. them. out. —@zoeinthecities To the families of those who died in the synagogue shooting in Pittsburgh, my deepest and sincere sympathies. This horror is escalating day by day. If only we had LEADERSHIP that would actually take steps to stop it. —@BetteMidler

U.S. President Donald Trump, who told reporters Saturday following news of the shooting that an armed guard at the Tree of Life synagogue could have changed the outcome, was also criticized.

"The fact is if there was no guns at all, there wouldn't have been a shooter in the first place," Slow Hands singer Niall Horan told his nearly 40 million Twitter followers. "Get a grip."

Trump kept saying in his chat with reporters that if there was an armed guard inside the synagogue that the “numbers” would have been a lot lower . The fact is if there was no guns at all , there wouldn’t have been a shooter in the first place. Get a grip —@NiallOfficial Here is <a href="https://twitter.com/realDonaldTrump?ref_src=twsrc%5Etfw">@realDonaldTrump</a> blaming the synagogue for allowing its members to get shot and killed.<br><br>On November 6th vote for everyone running against the people who prop him up. <a href="https://t.co/tJ0Z01im4T">https://t.co/tJ0Z01im4T</a> —@wkamaubell

Former House of Cards showrunner Beau Willimon attacked Republicans for a lack of action on gun laws — sentiments that have been echoed by much of left-leaning Hollywood for years.

Veteran American journalist Dan Rather said "all who excuse, abet, or stand in silence while hate is stoked for political gain" have a hand in the country's recent tragedies and TV personality Piers Morgan questioned the need for civilians to have rifles like an AR-15, one of the weapons used in the attack. The majority of American states do not have bans on assault weapons.

If you think your “prayers” absolve you from taking ANY action whatsoever, then they aren’t prayers, they are curses. Your party has cursed us for far too long. You need to be removed from power. And you will be, starting November 6th. <a href="https://t.co/86HSiprnyz">https://t.co/86HSiprnyz</a> —@BeauWillimon Mass murder at a Pittsburgh synagogue. A killer targeting African Americans in Kentucky. The bomb maker. The focus should not be only on Trump, but all who excuse, abet, or stand in silence while hate is stoked for political gain. —@DanRather Pittsburgh shooter is reported to have used an AR-15, the preferred weapon of choice for most mass shooters in America (Sandy Hook, Vegas etc) because they kill lots of people very fast. <br>This is what they look like.. <br>I ask again: why the f*ck are these legal for civilians? <a href="https://t.co/5ycMv464ly">pic.twitter.com/5ycMv464ly</a> —@piersmorgan

I Feel Pretty star Amy Schumer, who often gets political on her social media accounts, kept her post neutral as did talk-show host Ellen DeGeneres.

Schumer said her "heart is broken" by the shooting, with DeGeneres sending a message of love, saying "We all need love. We all want comfort. Let's give it to each other."

Today, I send out love to each and every one of you reading this. Every single one of you. We are one world. We all need love. We all want comfort. Let’s give it to each other. —@TheEllenShow My heart is broken for the victims and loved ones of everyone affected by the shooting at the Tree of Life synagogue in Pittsburgh <a href="https://t.co/IuMRo5S674">https://t.co/IuMRo5S674</a> —@amyschumer

At a hockey match in Vancouver between the Canucks and Sidney Crosby-led Pittsburgh Penguins Saturday evening, the teams observed a moment of silence to pay tribute to shooting victims.