Did Sterling threaten wife's attorney?

• Shelly Sterling reached an agreement to sell the Clippers


• Source: There are "clear indications of threatening behavior"


• Shelly Sterling is asking the court to uphold her deal

(CNN) -- Donald Sterling's estranged wife will ask a probate court judge Thursday to issue an order protecting witnesses from possible intimidation from Sterling, a source with knowledge of the situation has told CNN's Brian Todd.

Shelly Sterling recently reached an agreement with former Microsoft CEO Steve Ballmer to sell the Los Angeles Clippers, which is owned by a family trust, for $2 billion. The NBA ordered the sale of the team after Sterling's recorded racist remarks to a companion were made public.

Asked whether Donald Sterling or anyone on his side gave specific signs of intimidation, the source said there are "clear indications of threatening behavior." However, the source said it's not a case of "hired guns or goons."

The source would not say which witnesses might be intimidated, but said that will be clear when court proceedings are finished.

CNN's attempts to reach Donald Sterling's attorney for a response Wednesday night were not immediately successful.

A Los Angeles probate court will hold a four-day trial on the proposed sale to Ballmer, beginning July 7. Shelly Sterling is asking the court to uphold her deal with Ballmer.

NBA commissioner Adam Silver banned the Clippers' co-owner for life and fined him $2.5 million after the comments went public. Sterling responded by suing the NBA for $1 billion.

The real estate mogul bought the Los Angeles Clippers in 1981 for about $12 million.