A small airplane was spotted flying over the ESPY Awards with a mysterious message aimed at Prince Harry as he readies to 

The Duke is set to controversially win the Pat Tillman Award, a military honor, on Thursday night, but around an hour before the event began a plane was circulating overhead with a banner aimed at the royal. 

'Prince Harry: Investigate Mumis Death', the cryptic message read. 

It is unclear what the intention of the message was, or who paid to fly it around Hollywood before the glitzy event. 

A small airplane was spotted flying over the ESPY Awards with a mysterious message aimed at Prince Harry, urging him to 'investigate Mumis death'

A small airplane was spotted flying over the ESPY Awards with a mysterious message aimed at Prince Harry, urging him to 'investigate Mumis death' 

The Duke, 39, is set to scoop the Pat Tillman Award on Thursday evening, despite some critics feeling he is not a worthy recipient of the military honor

The Duke, 39, is set to scoop the Pat Tillman Award on Thursday evening, despite some critics feeling he is not a worthy recipient of the military honor 

It comes as the spotlight has fallen on Harry as he readies to win the award, and he is set to collect the gong at Los Angeles' Dolby Theatre. 

Tennis legend Serena Williams led stars out on the red carpet early on Thursday evening, ahead of her hosting duties at the event. 

Williams cut a glamorous figure as she graced the red carpet in a silver and black gown, and wore her light blonde tresses in bouncy waves.

It comes weeks after Tillman's mother Mary scathed Harry's win in her son's honor. 

Mary told DailyMail.com last month that she was 'shocked' her son's award would go to 'such a controversial and divisive figure.' 

She also claimed that she was not even consulted over the winner, as she told the Mail there are other 'recipients that are far more fitting.' 

'These individuals do not have the money, resources, connections or privilege that Prince Harry has. I feel that those types of individuals should be recognized,' she said. 

Thursday evening's host Serena Williams stunned in a form-fitting silver and black gown as she hit the red carpet before the glitzy event

Thursday evening's host Serena Williams stunned in a form-fitting silver and black gown as she hit the red carpet before the glitzy event 

Pat Tillman's mother Mary criticized the decision to hand Prince Harry the award in her son's honor, saying she was 'shocked' it would go to 'such a controversial and divisive figure

Pat Tillman's mother Mary criticized the decision to hand Prince Harry the award in her son's honor, saying she was 'shocked' it would go to 'such a controversial and divisive figure 

Harry is set to win the Pat Tillman Award, named for the former NFL star who left his lucrative career to enlist in the army after 9/11, before he tragically died in Afghanistan in 2004

Harry is set to win the Pat Tillman Award, named for the former NFL star who left his lucrative career to enlist in the army after 9/11, before he tragically died in Afghanistan in 2004 

The award is named for Pat Tillman, a former NFL star who left his lucrative career to enlist in the army after 9/11, before he tragically died in Afghanistan in 2004.  

ESPN quickly defended its decision to give the award to Harry following Mary's remarks, saying it chose the Duke of Sussex ‘specifically for the work of The Invictus Games Foundation.’